1. Concepts
A load balancer is a device that acts as a reverse proxy and distributes network or application traffic across a number of servers. It helps scale horizontally across an ever-increasing number of servers.
2. How does the load balancer work?
Define IP or DNS name for LB: Administrators define one IP address and/or DNS name for a given application, task, or website, to which all requests will come. This IP address or DNS name is the load balancing server.
Add backend pool for LB: The administrator will then enter into the load balancing server the IP addresses of all the actual servers that will be sharing the workload for a given application or task. This pool of available servers is only accessible internally, via the load balancer.
Deploy LB: Finally, your load balancer needs to be deployed — either as a proxy, which sits between your app servers and your users worldwide and accepts all traffic, or as a gateway, which assigns a user to a server once and leaves the interaction alone thereafter.
Redirect requests: Once the load balancing system is in place, all requests to the application come to the load balancer and are redirected according to the administrator’s preferred algorithm.
On this page.
3. Types of LBs
Load balancers are generally grouped into two categories: Layer 4 and Layer 7.
Layer 4 load balancers
It acts upon data found in network and transport layer protocols (IP, TCP, FTP, UDP). They are mostly the network address translators (NATs) which share the load to the different servers getting translated to by these load balancers.
Session persistence can be achieved at the IP address level
No termination for TCP connections
The 2 modes of L4 LB
Layer 7 load balancers
